CVE-2026-8426 Details
Description
Concrete CMS 9.5.0 and below does not validate a CSRF token before processing requests to /dashboard/extend/update/prepare_remote_upgrade/<remoteMPID>. An attacker who controls the remote package returned for a known marketplace item ID can overwrite the package PHP on disk and force its upgrade() method to execute in a single browser navigation. This results in remote code execution as the web server user. In order to be vulnerable, the victim must be passing canInstallPackages, victim site must be connected to the Concrete marketplace; and the attacker controls the package returned for a marketplace item ID already installed on the victim site. The Concrete CMS security team gave this vulnerability a CVSS v.4.0 score of 7.5 with vector CVSS:4.0/AV:N/AC:H/AT:P/PR:N/UI:A/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N. Thanks https://github.com/maru1009 for reporting.
A Cross-Site Request Forgery (CSRF) vulnerability has been identified in Concrete CMS versions through 9.5.0. The issue arises because the application does not validate CSRF tokens before processing requests to prepare remote upgrades for installed marketplace packages. An attacker controlling the remote package can overwrite the package's PHP file on disk and execute its upgrade method, leading to remote code execution as the web server user. To exploit this vulnerability, the victim must have the 'canInstallPackages' permission, be connected to the Concrete marketplace, and have a vulnerable package installed from the marketplace.
Users can upgrade to Concrete CMS version 9.5.1 or later, where this vulnerability has been fixed.
Metrics
CVSS 4.0 Severity and Vector Strings:
CVSS 3.x Severity and Vector Strings:
No data available for CVSS Version 2.0 on this CVE.
CISA-ADP
Assessed May 22, 2026References to Advisories, Solutions, and Tools
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| URL | Source(s) | Tag(s) |
|---|---|---|
| https://documentation.concretecms.org/9-x/developers/introduction/version-history/951-release-notes | ConcreteCMS | Release Notes |
Weakness Enumeration
| CWE-ID | CWE Name | Source |
|---|---|---|
| CWE-352 | Cross-Site Request Forgery (CSRF) | ConcreteCMS |
| CWE-829 | Inclusion of Functionality from Untrusted Control Sphere | ConcreteCMS |
Affected Products
| Product | Versions |
|---|---|
| concretecms concrete cms | < 9.5.1 |
CPE
Remediation
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Change History
5 change records found show changes
| Date | Action | Recorded By |
|---|---|---|
| Jul 23, 2026 | CVE Translated | [email protected] |
| Jun 17, 2026 | CVE Modified | ConcreteCMS |
| Jun 17, 2026 | CVE Modified | CISA-ADP |
| May 26, 2026 | Initial Analysis | [email protected] |
| May 21, 2026 | New CVE Received | ConcreteCMS |